As a refrigerant compressor that houses a compression mechanism for compressing refrigerant and a motor for driving the compression mechanism in a sealed vessel, there is a refrigerant compressor of high-pressure chamber system in which a pressure in the sealed vessel serves as a discharge pressure for refrigerant. However, in the refrigerant compressor of high-pressure chamber system, since a temperature and a pressure becomes high in the sealed vessel, there is a problem that a coil temperature of a motor increases to degrade motor efficiency of the motor, such as a motor using a general ferrite magnet.
On the other hand, there is a refrigerant compressor of low-pressure chamber system in which a pressure in the sealed vessel serves as a suction pressure for the refrigerant. In the refrigerant compressor of low-pressure chamber system, a motor can be cooled with sucked refrigerant having a low temperature and a low pressure. However, since cooling the motor by the refrigerant sucked into the sealed vessel causes density of the refrigerant (gas) to be decreased, there is a problem that circulation amount of the refrigerant circulating in the refrigeration cycle is reduced to lower the refrigeration capacity, and further to lower the efficiency of the refrigeration cycle too. Therefore, in the refrigerant compressor of low-pressure chamber system, a structure is employed that introduces the sucked refrigerant to a compression mechanism without receiving a thermal influence from the motor.
For example, in Japanese Patent Application Publication No. S63-50695, there is a description as “according to the present invention, the inside of a closed casing 1 is partitioned by a compressor part 5, a suction pipe 20 is provided in the closed casing 1 in the part facing a motor part 2 side of an axial through-hole 16 in a shaft 15 coupling a roller 6 in the compressor part 5 with a rotor 4 in the motor part 2, and a suction hole 19 is provided for introducing suction gas into the compressor part 5 through the through-hole 16, to introduce suction gas into the compressor part 5 side without contacting heat from the motor part 2 for the gas to be subject to gas-liquid separation then to be sucked into a cylinder chamber through the suction hole 19.” (see page 2, lower right column, lines 5-14).
In addition, in Japanese Patent Application Publication No. H09-236092, there is a description as “an gist of the second invention is to provide a hermetic compressor, for use in a refrigeration apparatus, that allows refrigerant gas to be sucked into a sealed housing, which incorporates a compression mechanism and its driving motor, for the compression mechanism to suck it, and includes a liquid injection circuit for injecting a part of the liquid refrigerant into a compression chamber of the compression mechanism, which is characterized in that a suction pipe of the refrigerant gas is connected to the sealed housing at a position where the refrigerant gas is directly introduced to the compression mechanism, and the liquid injection circuit is branched to connect one of them to a position where the liquid refrigerant is injected toward the motor (see paragraph 0015).